The invention relates to improvements in apparatus for surface treatment (such as deburring, cleaning or polishing) of metallic, plastic and/or other workpieces. More particularly, the invention relates to improvements in apparatus of the type disclosed in commonly owned U.S. Pat. Nos. 4,218,854, 4,368,599, 4,757,647 and 4,844,232. The disclosures of these patents are incorporated herein by reference. Apparatus of the type to which the present invention pertains are also disclosed in published European patent applications Nos. 205 738 and 289 845.
Commonly owned U.S. Pat. No. 4,844,232 discloses an apparatus wherein the shell of the cage-like receptacle for workpieces is composed of longitudinally extending cable-like, rope-like, wire-like or rod-like components. The end portions of the components are secured to two end walls which act not unlike wobble plates or swash plates and cause the components to move back and forth in parallelism with the axis of rotation of the receptacle to thus advance the workpieces in the interior of the shell in a direction from the one toward the other axial end of the receptacle. As shown in FIG. 4 of this patent, the connections between the end portions of the components and the end walls include ball joints. Each ball joint includes a socket having a concave surface and a spherical head which extends into the socket and is biased against the concave surface. A drawback of such joints is that they are expensive as well as that their parts are subjected to extensive wear when the apparatus is in use. Moreover, such joints are overly affected by certain treating agents for the workpieces in the shell of the receptacle, for example, by certain types of fluids or by certain flowable pulverulent and/or granular solid materials which are propelled against the workpieces to remove burrs, to achieve a certain surface finish and/or for other purposes. Solid particles which penetrate between the socket and the head of a ball joint are likely to rapidly damage or totally destroy the joint. Once a joint fails to function, the respective component is subjected to pronounced bending or flexing stresses whenever the apparatus is put to use, and such repeated flexing causes the material of the component to tire so that the component breaks shortly after partial or complete destruction of the respective ball joint